A Southland woman's emails to friends from her workplace computer indicating she was slacking on the job have rebounded to bite her.

Bridgett King, a former employee of J&R Pumps Southland, which trades as Waterforce, claimed she was required to work excessive overtime in order to complete her duties.

She took her case to the Employment Relations Authority, but lost after evidence she had emailed her friends from work saying she had done "bugger all work all day" and was "just f...ing around" because her boss was away.

The written decision of authority member Eleanor Robinson says Ms King claimed she was required to work excessive overtime in order to complete her duties.

Despite raising this matter on several occasions with her employer Ms King claimed her workload was not reduced and she became stressed and had no option but to resign from her job.

Her individual employment agreement said she had to work any additional hours required above her standard 45 hours a week; no extra payment would be made for those additional hours.

Waterforce denied Ms King's claims, saying she had breached her employment agreement by refusing to work to the required standard and by voluntarily terminating her employment without giving the required notice.

Authority member Ms Robinson's decision says that, contrary to Ms King's assertion that her workload required her to work excessive overtime, which made her feel tired and stressed, the emails she sent had indicated she was an employee with an active and positive social life.

"The emails also indicated an employee who rather than feeling stressed was prepared to shirk work when her manager was absent, was disengaged from her job and looking for alternative employment," the decision says.

The authority also did not accept the claim by Ms King that the overtime she worked was excessive and she was unable to take time off in lieu.

"I do not find that there was a breach of duty on the part of Waterforce. I determine that Ms King was not unjustifiably constructively dismissed from her employment, but that she voluntarily resigned," the decision says.

Several other of Ms King's complaints were also dismissed by the authority. It also said Ms King breached her employment agreement by failing to work out her notice.

However, the authority also found that Ms King was unjustifiably disadvantaged by an instruction to move her desk into her manager's office.

It accepted that Ms King found the request degrading and ordered Waterforce to pay her $500.